This invention relates generally to thermo electric coolers and temperature sensors and more particularly concerns a circuit for a thermoelectric cooler and a temperature sensor which is able to monitor and provide accurate temperature control of the thermoelectric cooler.
A single beam laser diode assembly has a single diode and usually, in a scanning system, the diode is driven by a train of image pixel information. The pixel information is used to drive the diode and therefore stimulate laser flux emission where there is a white pixel in a write white system. In a write white system, a laser is turned on to create white space on a page. Intensity of the light beam is directly proportional to the output power of the laser. In order to keep the output power of the diode constant, the temperature of the diode should be kept at a constant level. However, due to the structure of the laser diode assembly, as the pixel information changes, which causes the diode to turn on and off, the temperature of the diode fluctuates, which in turn causes the output power of the diode and the intensity of the light beam to fluctuate. In a printing, system fluctuation in the intensity of light beams causes fluctuation in the exposure of a printed pixel.
A multiple beam diode assembly has at least two diodes in close proximity on a common substrate. Each diode is driven by a separate train of image pixel information. Again, as the pixel information changes, the temperature of each diode fluctuates. However, in a multiple diode system, the changing temperature of a diode also causes a temperature fluctuation in adjacent diodes. The temperature fluctuations of the adjacent diodes cause the output power and the intensity of the light beams in those adjacent diodes also to fluctuate.
A tri-level system may use one or more diodes with at least one diode operating at full on, full off, and partially on. One example of an application using a single diode tri-level system is the printing of black and white documents with a highlight color. Tri-level systems suffer from the same heating effects both in the full on and the partially on modes of the laser.
Accordingly, it is the primary aim of the invention to provide a method for quickly compensating for a variety of thermally induced effects. Further advantages of the invention will become apparent as the following description proceeds.